Conformational Analysis of Astrochemically Relevant Molecules Using Rotational Spectroscopy

Abstract

Rotational spectroscopy was employed to investigate the conformational preferences and internal dynamics of two sulfur-containing organic molecules, allyl phenyl sulfide (APS) and 2-methylthioethylamine (2-mtea). Supersonic jet-cooled Fourier transform microwave (FTMW) Spectroscopy, supported by quantum chemical calculations, enabled the identification and characterization of low-energy conformers for both systems. The analysis of hyperfine structure due to the 14N nuclear quadrupole coupling and internal methyl rotation in 2-mtea provided detailed insights into the electronic and structural effects of sulfur and nitrogen substitution. Natural bond orbital (NBO) analysis revealed key orbital interactions between the lone pairs of sulfur and nitrogen, and the various organic side chains that govern conformational stability. These findings contribute to a deeper understanding of the conformational behavior of S and N containing organic molecules, which are of growing interest in astrochemical contexts.